A comparative analysis of AC/DC transfer standards for comparison of national standards

Valentyn Isaiev,Oleh Velychko

doi:10.15587/1729-4061.2018.150459

Abstract

The development of standards based on quantum effects, in particular, alternating voltage synthesizers, has not yet allowed defining the metrological characteristics of measuring instruments for alternating voltage up to 1,000 V at a frequency up to 1 MHz. Therefore, a comparative analysis of international comparisons of national standards has summarized the possibilities of metrological support with the use of AC/DC voltage transfer standards.The conducted analytical and experimental studies give grounds to state the decisive contribution of national metrological institutes in the formation of the modern equivalence level of AC/DC voltage transfer standards. A comparative analysis of the uncertainty of measurements achieved by the leading national metrology institutes has made it possible to distinguish the most accurate type of thermal voltage converters based on the thermocouples connected in series. Such a measuring instrument allows measuring AC/DC transfer difference with an uncertainty of less than 1 μV/V at certain points of the measuring range.Consideration of the capabilities of the travelling standards to ensure a stable storage of a value of AC/DC voltage transfer difference has indicated the advantage of the thermal converter of an indicated above type, relative to the other types used in the comparisons of AC/DC transfer standards. The calculation of stability coefficients for different types of standards has shown an approximately twofold advantage of thermal converters based on the thermocouple comparing with multi-range thermal comparators on the basis of the root-mean-square voltage sensor. The results of the considered comparisons have shown that there were no advantages of any of the measurement schemes used by the laboratories since no relation has been found between the reported measurement uncertainty and the scheme.The results of the estimation of the frequency influence of the input voltage on the transformation coefficient of the AC/DC voltage transfer standards of the two types have given the grounds to neglect correcting the contribution of this source of uncertainty. The proposed approach to measuring the AC/DC transfer difference with providing the connection with a direct definition allows us to estimate more appropriately this metrological characteristic in two ways

Highlights

With the introduction of the scientific discovery of the Josephson Effect into the applied metrology, the researchers reached the quantum accuracy of reproduction of a direct voltage of up to 10 V [1]
The analysis showed that the appropriate level of reproduced voltage by means of such standards for the metrological support of laboratory measuring instruments (MI) has not yet been achieved, despite the significant progress in the development of primary standards on the basis of the Josephson Effect
– estimating the influence of the frequency of the input voltage on the transfer coefficient of a planar type voltage thermal converter on the basis of the thermocouples connected in series and a thermal comparator based on the sensor of the input RMS voltage

Summary

Introduction

With the introduction of the scientific discovery of the Josephson Effect into the applied metrology, the researchers reached the quantum accuracy of reproduction of a direct voltage of up to 10 V [1]. Such reproduction systems have a good capability for metrological support of solid state DC voltage standards, for example, on the basis of Zenner’s diode, with an uncertainty of measurements (UM) less than 1 μV/V. The validation of the engineering design development of the standards on the basis of the mentioned quantum effect has been performed It showed the level of equivalence of the two standards with different methodological approaches at the level of 10 nV/V [3]. The results of the comparison of two standards of the alternating voltage unit on the basis of the quantum effect at 1 V voltage at a frequency of 100 Hz, when a level of equivalence of less than 0.1 μV/V was achieved, have been recently published [5]

Objectives

Discussion

Conclusion